Magnetron



April 26, 1938. K. FRITZ ET AL MAGNETRON Filed April 7, 1957 2 Sheets-5h96?. l

l I I l lll W IIMII Ua BY Il INVENTORS KARL FRITZ AND UDOL F v RADINGER /Wcm ATTORNEY April 26, 1938. K Fmfz ET AL 2,115,521

MAGNETRON Filed April '7, 1937 2 sheets-sheetl 2 I N VEN TOR S o KARL FRITZ/WD a BY RUDOLF v. RAD/Neff? M/ mfa/ +l/a 1+ 1 i+1/a ATTORNEY Patented Apr. 26, 1938 UNITED STATES PATENT oFFlcE MAGNETRN Application April -7, 1937, Serial No. 135,372 In Germany April 30, 1936 9 Claims.

The present invention relates to electron discharge devices of the so-called magnetron type and has for its principal object the provision of frequency determining means for such tubes comprising a shielded concentrically symmetrical oscillatory circuit. The electron discharge device is inserted in the oscillatory circuit.. In a modiilcation of the invention, means are disclosed by which the natural wave of this oscillatory circuit can be gradually varied.

It is known that tuned circuitsof poor radiation can be obtained by disposing a casing as part of the oscillatory circuit symmetrically around the other current carrying parts, and connecting this casing with the other parts so that the current iiowing in the oscillatory circuit is uniformly distributed over the entire casing. In these oscillatory circuits no outer electrical or magnetic ileld can develop.

Short wave tubes are also known in which the lrenuency determining oscillatory circuit cornprises two coaxial tubes, these tubes containing the electrodes as parts. The electrodes, or the parts acting as electrodes are situated in the centerV oi the two cylinders. The axial length of the tube is approximately equal to one wave length. In the usual known tubes moreover, there is n way of varying the natural wave.

nc compared with conventional tubes, the tube according to .the invention has the advantage that its axial length is considerably shorter. The

f ral frequency of the oscillatory circuit can `be varied.

The short wave tube, and more particularly the magnetron tube according to the invention, and in conjunction with a concentrically symmetrical oscillatory circuit of poor radiation, comprising two coaxial cylinders within which the discharge system is arranged, is characterized by the fact that the oscillatory circuit is completely shielded at its outer circumference except for the lead-ins for the operating voltages, and the outgoing connections for the high frequency, that the two cylinders are connected with each other at their ends as regards high frequency, that the innermost cylinder is opened approximately in the center, and that the separated surfaces (Cl. Z50-27.5)

form the anodes of the discharge system. Ordinarily. the inner cylinder will be so opened that the separated surfaces-are at a nite distance from each other, forming preferably parts of a cylindrical surface, the cathode being placed at the axis of the cylinder.

Preferably the separated faces are conned by parts of a. cylinder surface the axis of this cylinder extending perpendicular to the axis of the oscillatory circuit.

In view of the fact that the concentrically symmetrica] oscillatory circuit is closed. more especially directly closed along the outer circumference as regards high-frequency, it is possible in a simple manner to resort to measures and to provide means whereby the natural frequency of the oscillatory circuit can be varied from the outside.

The novel features whichwe believe to be characteristic of our invention are set forth with particularity in the appended claims, but the invention itself vwill best be understood by reference to the following description taken in connection with the accompanying drawings in which Figure 1 is a schematic perspective of an oscillatory circuit arrangement embodying the principle of our invention, Figure 2 is a longitudinal section of a tube and circuit schematically shown and embodying our invention, Figures 3 to 6 inclusive and Figure 10 are sections of modifications schematically shown of the tube and circuit shown in Figure 2 with tuning arrangements, Figures '1, 8a, and 8b show diagrammatically the cathode and circuit arrangements in a tube embodying our invention, Figures 9a and 9b are diagrammatic representations of means of coupling a tube and circuit made according to our invention to an output device, Figure ll is a diagram illustrating a method of voltage application to a tube of the kind shown in Figure 10, and Figure l2 is a schematic showing of a means for varying the oscillating frequency of a tube and circuit made according to our invention.

The principal structure of the oscillatory circuit employed will now be described in reference to Figures 1 and 2.

Figure 1 shows an oscillatory circuit of poor radiation and concentrically symmetrical with respect to the axis R, such as is known in general. The inductance of this circuit is formed by the outer conductor La and parts of the inner conductor L1. The capacitance is represented by two circular disks C1 and C2 arranged at the inner ends of the legs of the inner conductor parts Li.

Figure 2 shows in principle a tube according to the invention. Two cylinders L. and L1 are electrically connected to each other and their ends closed by members St ringlike in form. The inner cylinder L1 which may be a solid cylinder, is opened up approximately at the center of the tube. The cathode K is arranged laterally to the place of separation or in the center between the separated surfaces A1 and Az. In the case represented the separated surfaces form parts of a cylindrical surface whose axis extends perpendicular to the central axis of the oscillatory circuit comprising the inductances L. L1 and the capacitances existing between surfaces A1, Az. Magnets M outside the casing provide a magnetic field parallel to the cathode K.

In the tube shown in Figure 3, the oscillatory circuit consists of a fixed part containing the discharge system comprising cathode K. and anodes A1, Az, and the central parts L'1 and L. of the coaxial cylinders, and of one or two parts L" and L" movable in the axial direction, and which reach in a cap-like manner over the open 'ends of the fixed central part and have coaxial inwardly extending tubular extensions T, T cooperating with the inner tubular member. The actual discharge space is closed up in a gas tight manner from the outer space by a tubular envelope G. the envelope being coaxial with the tubular members L'. and Li. The ends of the envelope G are sealed to the inner tubular member L1. 'I'he mechanical connection between the inner part L'1 and the outer part L. for supportingthese parts in spaced relationship is established by the envelope G and the insulation support O arranged for instance in a ring about the inner part. By suitable means the movable parts can be displaced in the direction of the arrows P whereby the operating wave length can be varied, or the cap like members may be threaded to engage threads on the outside of the outer tubular members.

Figure 4 shows a similar tube. It comprises only two telescoping tubular parts L1 L'., and L1 L." which can be turned relative each other. '111e movable parts engage each other in a sleeve like manner at the circumference of the outer cylinder. 'Ihese overlapping parts may be threaded at W. The tube envelope G is a tubular member coaxial with the tubular members L1 and L1 and is closed at its ends, the ends being sealed to the tubular members L'i.

In the tubes according to Figures 5 and 6 the oscillatory circuit consists of a mechanically rigid unit. About the separated parts L1 and Lz of the inner cylinder but outside the discharge system, metal parts M or dielectric D are pro- .vided by means of which the resultant capacity between the separated faces can be varied, more especially increased.

Figure 5 shows a tube of the above mentioned type. 'I'he arms of the inner cylinder have arranged thereon two metal shields M having the shape of a cone surface or spherical cup, such that the openings having the largest diameter are situated opposite each other approximately above the discharge path. The metal shields terminate into hollow cylinders H which can be moved in axial direction on the arms of the inner cylinders. The rods V represent the adjusting rods for moving the movable parts and extend through and are guided along a slot in the inner cylinder. The tubular glass envelope G is sealed to the tubular members L1 and Lz in the same manner as shown in Figures 3 and 4.

In the tube shown in Figure 6, for the purpose of varying the wave length, a cylinder D is placed over the two arms of the inner cylinder, this cylinder D being composed of adjacent cylinders having any desired diameter. In order that, especially in case of equal diameters, a variation in the capacity might be obtained, the individual partial cylinders are made of materials with different dielectric constants. In the forms of applicants invention shown in Figures 6 and 'I the inner and outer tubular members L.. and L1 and La are closed and joined at their ends to form the envelope of the tube. The members L., L1, and In are preferably tubular members which are cylindrical in cross section. the inner ends of the tubular members L1 and La being formed to provide the anode segments A1 and Az.

Figures 7 and 8 show examples for suitably connecting the operating voltage sources.

In Figure '7, the plate potential Ua is applied yto the outer cylinder at any desired point W.

and the heating voltage is introduced at N of the outer casing or shield casing. Since with proper` assembling, no high frequency currents flow on the outer side of the casing of the oscillatory circuit, no potential differences exist between the individual points of the outer surface. Therefore, the plate potential can be applied to any desired place of the casing of the oscillatory circuit.

For the part of the heating circuit situated inside the oscillatory circuit the most accuratr` symmetry is of course required, otherwise undesirable compensation currents would flow across the heating lines.

Various propositions have already been madr` for arranging the heating line and filament coaxially to the inner cylinder of an oscillatory circuit of the mentioned type with relatively poor radiation. Figure 8a shows a suggested arrangement making use of an electromagnet M. 'I'he two anodes representing the parts of the inner cylinder L1 are oppositely disposed longitudinally. The filament and the heating current line are arranged in the axis of the inner cylinder. In these arrangements it is very diilicult to withhold high frequency currents from the filaments. High frequency compensation currents pass across the ordinarily high ohmic resistance of the filament K, which originate for instance at the anode A1 and pass across the natural capacity Cr', then'across the filament K and across the second capacity C1 to the anode Az. When passing through the filament K losses occur in accordance with the ohmic resistance of the filament, which increase the damping of the oscillatory circuit.

If for any reason'despite this condition it is desired to bring out the heating current lead-ins in the rotational axis of the oscillatory circuit, it is necessary to select an arrangement according to Figure 8b. According to the invention the lament K extends perpendicularly to the symmetry axis. The two lead-ins are bent into an angle and are arranged to pass in front of the front faces of the anodes, and are then brought out in the axis.

To prevent any high frequency leaks towards the outside, the heating lead-ins after leaving the discharge chamber are choked by means of chokes X, or made to undergo proper damping. At the ends of the inner cylinder L1 capacitances C are suitably placed between the heating lines and the casing of the oscillatory circuit. In this case the high frequency losses are confined to the illaments proper. 4

Figures 9a and 9b show two examples for connecting radiators. The radiator S' is current coupled. The course of the current is indicated in dash lines. The radiator S" is voltage coupled. The connection with the outer surface of the inner cylinder Li is established in a capacitive manner for instance by means of two capacitive surfaces F.

Figure 10 shows a construction slightly deviating from the idea of the invention. The parts of the inner cylinder Li instead of being directly connected with the outer cylinder are capacitively connected with the movable parts L", L'" of the outer cylinder. The distances between the ends ofthe inner parts L; oscillating so to say, as dipoles having the length M2, and those of the movable outer parts L" and L" are variable. In order to obtain a definite course of the ileld lines, the movable parts may be provided with attachments Z.

The application of the voltage to these dipoles involves /ii general somewhat greater diiiiculties. A relatively simple solution resides in connecting the plate potential source to the voltage nodes of the inner parts L1 and choosing the length of the line up to the outer shield casing L.. approximately 7i/4+11..A/2, whereby 11:0, l,`2, 3 etc. as shown in Figure 11. v

The idea of the present invention is in no way limited to the examples of construction as described and shown in` the drawings. If required, auxiliary electrodes may be inserted between the cathode and the anodes. 'Ihe forms of the oscillatory circuits, and more especially the measures and means for varying the natural frequency are in their application not limited to magnetron tubes, but may also be used in tubes which are operated without magnetic eld.

If the tube is to be used in conjunction with a. radiator, it will often be desirable to enclose the latter within an envelope. 1f in view of reasons in the construction, this solution is not possible, the radiator can be used apart from the tube. and the energy can be supplied across a special line, or capacitively or inductively through the glass wall.

It is advisable to use non-magnetic material for the outer cylinder, since at operation of the tube in a magnetron circuit, the field lines of the magnetic field must permeate the outer cylinder,

in order to be permitted to act upon the discharge path situated in the interior.

The possibility of varying the operating wave length (natural frequency of the oscillatory circuits) is not confined tothe examplesV herein shown. 'Ihe movable parts M or D may also be shaped differently within the oscillatory circuit, and may be operated by a lever drive, and may be brought outside through sprlngy sealing-in parts such as glass springs Q as shown in Fig- What we claim as new is:

1. An electron discharge device for use at high frequencies and including a pair of concentric tubular members electrically connected at their ends, the inner tubular member being mechanically separated at the middle and formed to provide a pair of oppositely disposed anode segments, a cathode positioned between said anode segments and means for providing a magnetic eld parallel to said cathodeand anode segments.

2. An electron discharge device for use at high frequencies including a pair of concentric tubular members of-predetermined length electrically connected at their end's, the inner tubular member vbeing mechanically separated at the middle and formed to provide a pair of oppositely disposed anode segments transverse to the longitudinal axis of said tubular members, a straight thermionic cathode positioned between and co-axial of said anode segments and means for providing a magnetic field parallel to said cathode and anode segments. l

3. An electron discharge device for use at high frequencies and including a pair of concentric tubular members electrically connected at their ends by solid iiat ring-like members to enclose the space between the tubular members, the inner tubular member being mechanically separated at the middle and formed to provide a pair of oppositely disposed anode segments, a cathode positioned between said anode segments and means for providing a magnetic iield parallel to said cathode and anode segments.

4. An electron discharge device for use at high frequencies and including a pair of concentric tubular members and means for electrically connecting the tubular members at their ends and including a cup-shaped member, the inner tubular member being mechanically separated atA the middle and formedvto provide a pair of oppositely disposed anode segments, a cathode positioned between said anode segments and means for providing a magnetic eld parallel to said cathode and anode segments, said cup-shaped member being movable longitudinally of said tubular members to vary the natural frequency of oscillation of the electron discharge device.

5. An electron discharge device for use at high frequencies and including a pair of concentric tubular members, means for electrically connecting the tubular members at their ends and including a cup-shaped member having a coaxial tubular extension cooperating with the inner tubular member, the Vinner tubular member being mechanically separated at the middle and formed to provide a pair of oppositely disposed anode segments, a cathode positioned between said anode segments and means for providing a magnetic ileld parallel to said cathode and anode segments, said cup-shaped member being movable longitudinally of said .tubular members to vary the natural frequency of oscillation of the electron discharge device.

6. An electron discharge device for use at high frequencies and including a pair of concentric tubular members and means for electrically connecting the tubular members at their ends and including a cup-shaped member having a coaxial tubular extension cooperating with the inner tubular member, the inner tubular member being mechanically separated at the middle and formed to provide a pair of oppositelydisposed anode segments, a cathode positioned between said anode segments and means for providing a magnetic field parallel to said cathode and anode segments, said cup-shaped member being movable longitudinally of said tubular members to vary the natural frequency of oscillation of the electron discharge device, and an envelope around a portion of the inner tubular member for enclosing the anode segments and cathode.

7. An electron discharge device for use at high frequencies including a pair of tubular concentric members and means tor electrically connecting the tubular members at their ends comprising a pair o! cup-shaped members, the inner tubular member being mechanically separated at the middle and formed to provide a pair oi oppositely disposed anode segments, a cathode positioned between said anode segments, and means for providing a magnetic eld parallel to said cathode and anode segments, said cup-shaped members being movable longitudinally of said tubular members to vary the natural frequency of oscillation of the electron discharge device.

8. An electron discharge device for use at high frequencies, including a pair of concentric tubular members electrically connected at their ends, the inner tubular member being mechanically separated at the middle and formed to provide a pair 9i oppositely disposed anode segments transverse of the longitudinal axis of said tubular members, a cathode positioned between said tubular cathode and means tor providing a magnetic iield parallel to said cathode and anode segments. cup-shaped members having their open ends opposed and slidably mounted on said inner tubular member adjacent said anode segments and means for moving said cup-shaped members toward and from each other to vary the capacity between the separated ends of the inner tubular member.

9. An electron discharge device for use at high frequencies and including a pair'oi concentric tubular members electrically connected at their ends by solid ilat ring-like members to enclose the space between the tubular members, the inner tubular member being mechanically separated at the middle and formed to provide a pair of nppositely disposed anode segments transverse to the longitudinal axis of said tubular member, a cathode positioned between said anode segments and means for providing a magnetic eld parallel to said cathode and anode segments. cup-shaped members having their open ends opposed and provided with tubular extensions for slidably supporting the cup-shaped members on the inner tubular member adjacent the anode segments, and means for moving said cup-shaped members toward and from each other to vary the capacity between the anode segments. and an envelope enclosing said cathode and anode segments.

RUDOLF VON RADINGER. I0 

